Oral inhalation devices for dispensing medication from an aerosol canister into one's lungs are known to those skilled in the art as evidenced by the patents to:
______________________________________ Thompson, et al 3,732,864 Kropp 3,636,949 Armstrong, et al 3,789,843 Warren 3,814,297 Warren 3,826,413 Ciranna 3,605,738 Hanson et al 3,565,070 Brock 3,456,645 Phillips et al 3,456,646 Thiel 3,456,644 Alsop 3,302,834 Fowler 3,404,681 Mitchell et al 3,187,748 Paullus et al 3,157,179 ______________________________________
Inhalers of the type referred to above are provided with a mouthpiece arranged laterally respective to a housing within which a canister of medication is contained. Theoretically, the mouthpiece is received within one's mouth, and the canister is then depressed, thereby opening the canister valve and releasing the medication into the mouthpiece where the medication is admixed with air and flows into one's lungs. The timed sequence of depressing the canister and deeply inhaling through the apparatus is difficult for the average patient to achieve and consequently, the patient often fails to receive the proper dosage of medication deep down within his lungs.
Often the patient will depress the canister prior to inhaling thus releasing the drug too early for adequate transport to the small airways; or, otherwise, the patient perhaps will depress the canister halfway through the inhalation. In any event, this lack of synchronization between the patient's breathing cycle and the canister movement usually results in only 7-13% of the desired medication properly reaching the lungs.
Others have recognized this problem of synchronization between the patient and the inhaler device and have suggested the use of various different, complex, and expensive flow responsive valve means, as evidenced by some of the above listed patents. The present invention represents a giant step forward in the art for the reason that it provides a relatively inexpensive pressure responsive inhaler device which throttles flow from a canister into one's lungs in a new and unobvious manner.
It would therefore be desirable to have made available an inexpensive, dependable, pressure differential actuated valve means which controls the flow of medication into an oral inhaler mouthpiece so that the medication is dispensed during the entire inhalation, with the opening of the valve occurring substantially at the beginning of the inhaled breath and the closing of the valve occurring substantially at the end of the inhaled breath. Moreover, it would be desirable for the valve means to open and close while air is flowing through the inhaler device and into the patient's mouth, so that there is a minimum loss of medication at the beginning and end of the inhaled breath. Apparatus which achieves these desired results is the subject of the present invention.